Foraging decisions of Sandwich Terns in the presence of kleptoparasitising gulls

Eric Stienen, A Brenninkmeijer

    Research output: Contribution to journalA3: Article in a journal without peer review

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    Abstract

    We studied prey selection of Sandwich Terns (Sterna sandvicensis) in the presence of kleptoparasitising Black-headed Gulls (Larus ridibundus) on Griend, Dutch Wadden Sea, from 1992 to 1998. Most often, gulls robbed larger sandeels rather than herring from terns. Provided that one parent attends the chick, energy intake would be too low for the chicks' survival if exclusively fed on sandeel. By provisioning an increasing proportion of herring, parent terns could theoretically overcome a potential food shortage when the chicks grow older. However, the proportion of herring did not increase with age of chicks in most years. Instead, parents increased their foraging effort with the growth of their offspring. In years with high proportions of food loss, parents left their chicks unattended at the nest more often. In that way, parents were largely able to counterbalance food shortage of offspring. In 1992 and 1996, when diet composition was unfavorable and food losses to gulls were high, parents left their chicks unattended at the nest for 680% of the daylight period. It is argued that the present working level of parents might be higher than in the 1960s.
    Original languageEnglish
    JournalThe Auk: a quarterly journal of ornithology
    ISSN0004-8038
    DOIs
    Publication statusPublished - 2005

    Thematic list

    • Sea and coastal birds
    • Breeding birds

    EWI Biomedical sciences

    • B280-animal-ecology

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